Disposal of used catalysts poses a tremendous problem worldwide in terms of safety as well as environmental impact. Spent catalysts from various chemical processes contain potentially toxic material impregnated therein which can leach out into the environment. In addition, the handling of such spent catalysts during disposal also requires special efforts to ensure that potentially toxic chemical residues therein do not have an adverse impact on the personnel handling the disposal.
Fluid catalytic cracking (FCC) processes result in emission of carbon monoxide. As a result of this, there is considerable pressure on refiners, to reduce emissions of carbon monoxide from FCC regenerator flue gas and to dispose safely used catalysts. Reduction of carbon monoxide in some cases been achieved by the use of incinerators or carbon monoxide boilers. Although these serve the purpose, it involves substantial capital investment. Carbon monoxide boilers may create problem with respect to maintenance and repair. Whenever carbon monoxide combustion system is taken out for various reasons, there is increase in carbon monoxide emissions from the FCC regenerator. The disposal of used catalysts is done in many ways like down grading the material and using for other application or sent for metal recovery.
Therefore, in order to maintain the purity of stack gas within allowable limits, it has been thought necessary to have support carbon monoxide control systems or modify the operation of the whole FCC by use of an external agent to reduce emissions of carbon monoxide from FCC regenerator flue gas and also to utilize effectively the heat generated during the carbon monoxide combustion process.
U.S. Pat. No. 4,064,039 discloses a catalyst containing Pt or Re which improves carbon monoxide burning in regenerator dense bed. This patent describes the use of modified fresh cracking catalyst with platinum group metal.
U.S. Pat. No. 4,915,037 teach the use of low surface area porous support having surface area greater than 50 m2/g which contains silica, alumina, silica/alumina, Kaolin and mixtures containing Pt, Rh, that improves carbon monoxide oxidation.
Escardino et al (British Ceramic Transactions (1999), 98(4), 172-177) discuss the use of spent FCC catalyst for making 4A-Zeolite.
U.S. Pat. No. 4,148,751 describes the use of alumina supported platinum as better additive compared to Pt containing fresh FCC catalyst.
Notwithstanding the amount of material available in the prior art, there is still need for a combustion catalyst which can either be freshly prepared or comprise regenerated catalytic material from FCC processes which provides a good consistent carbon monoxide combustion level with better physical properties.